Method of controlling the water head of the working face in the shield method of construction

ABSTRACT

A method of controlling the water head of the working face in the pressurized-slurry sealed shield method of construction, said method of controlling the water head comprising the steps of detecting the water head of the working face with a pressure transmitter, transmitting said water head as an electric signal to a pressure regulator, comparing said electric signal with the set pressure at said regulator, converting the electric signal corresponding to the deviation between said first-named electric signal and said set pressure into a pressure signal, and transmitting said pressure signal from a controlling board as an excitation voltage to a variable-speed motor made up of an eddy current coupler and an induction motor to control the rotational speed of said motor, thereby changing the amount of water supplied by a pump.

llnite States Patent 1 Matsushima [4 1 Nov. 6, 1973 [75] Inventor:

[73] Assignee: Nishimatsu Construction Company Limited, Minato-ku,Tokyo, Japan 22 Filed: Sept. 22, 1972 21 Appl. No.: 291,359

Hiroshi Matsushima, Tokyo, Japan [56] References Cited UNITED STATESPATENTS 3,030,070 4/1962 Krauss ..4l5/1 3,635,575 1/1972 Cloup ...4l5/lFOREIGN PATENTS OR APPLICATIONS 1,136,361 9/1962 Germany 61/85 PrimaryExaminer.lacob Shapiro Att0rneyE. F. Wenderoth et a1.

[57] ABSTRACT A method of controlling the water head of the working facein the pressurized-slurry sealed shield method of construction, saidmethod of controlling the water head comprising the steps of detectingthe water head of the working face with a pressure transmitter,transmitting said water head as an electric signal to a pressureregulator, comparing said electric signal with the set pressure at saidregulator, converting the electric signal corresponding to the deviationbetween said firstnamed electric signal and said set pressure into apressure signal, and transmitting said pressure signal from acontrolling board as an excitation voltage to a Van'- able-speed motormade up of an eddy current coupler and an induction motor to control therotational speed of said motor, thereby changing the amount of watersupplied by a pump.

2 Claims, 1 Drawing; Figure bosom/Ava Patented Nov. 6, 1973 METHOD OFCONTROLLING THE WATER HEAD OF THE WORKING FACE IN THE SHIELD METHOD OFCONSTRUCTION This invention relates to a method of controlling the waterhead of the working face in the pressurized-slurry sealed shield methodof construction.

The water head of the working face must be constantly maintained at agiven pressure for preventing the caving in of the earth and sand in thepressurizedslurry sealed shield method. The method that was generallyemployed heretofore for controlling the water head of the working facewas that consisting of detecting the concentration of the muddy slurryin the exhaust line and to adjust the .degree of opening of the valvesof either the water supply line or the slurry exhaust line accordingly.However, the fluctuation of the pressure at the working face was greatin the case of this method due either to the inaccuracy of the detectionof the concentration or to the considerable time that was required untilthe valves were opened in response to the fluctuation of pressure. Inconsequence, the collapse of the working face or clogging of the slurryexhaust line was likely to occur to inevitably result in the stoppage ofthe construction work.

Accordingly, an object of the present invention resides in ensuring thatthe water pressure necessaryfor maintaining the stability of the workingface of the excavation is always maintained constant, thereby making itpossible to carry the management of the pressurized-slurry sealed shieldmethod safely and with certainty.

Other objects and advantages of the invention will become apparent fromthe following description.

I found that the foregoing objects of the present invention couldbe'achieved if consideration was given to coupling a variable-speedmotor to the water supply pump that delivers water to the. working faceand by varying the rotational speed of this motor and hence the amountof water supplied by the pump.

The present invention will now be specifically described by referring tothe accompanying drawing, which illustrates one mode'of practicing theinvention. in the drawing, the solid linesrepresent the pipelines, whilethe broken lines represent the electric wiring.

Referring to the drawing, (1) is the water supply pump driven by meansof an alternating-current variable-speed motor. The a. c. variable-speedmotor is made up of a three-phase squirrel-cage inductionmotor (2) andan eddy current coupler (3). Since this setup is so adapted that by theapplication of a directcurrent excitation to the excitation coil in theeddy current coupler (3), the torque of the induction motor (2) (inputshaft) is transmitted to the eddy current coupler (3) (output shaft),the rotational speed of the variablespeed motor can be continuouslyvaried by controlling the voltage of said d. c. excitation.

Water delivered by means of the water supply pump (1) enters the frontalcutter chamber (4). The soil excavated by the cutter (5) enters thechamber (4) where it becomes a muddy slurry and is discharged externallyof the tunnel by means of an exhaust pump (6) (The numerals 2' and 3'are respectively an induction motor and an eddy current coupler as inthe case with 2 and 3, above). Now, since there is a variation in theconcentration of the muddy slurry depending upon the amount of the soilexcavated in this case, the pressure inside: the frontal cutter chamber(4) fluctuates. This pressure is detected by a pressure transmitter (7)and is transmitted in the formof a d. c. electric signal to a pressureregulator (8). The regulator (8) compares the electric signal valuereceived from the pressure transmitter (7 with the set value of apressure setting device (9) appended to the regulator (8) and sends to apreamplifier (10) as an operating output a d. c. electric signal(including a P. l. D. action) corresponding to the deviation in theforegoing values to convert the electric signal. to a pressure signal.The pressure signal is transmitted via a controlling board 11) to theeddy current coupler (3) as an excitation voltage by which therotational speed of the variable-speed motor (2 plus 3) and the amountof water supplied by the pump (1) are controlled. t

On the other hand, a speed detecting generator (12) detects the speed ofthe eddy current coupler (3), and feeds back the detected speed asvoltage to the controlling board (11). The controlling board (11)compares the detected voltage with the set voltage, adjusts theexcitation voltage until there is no deviation in the two voltages andfunctions to maintain the established water pressure by varying therotational speed of the variable-speed motor (2 plus 3) and the amountof water supplied by the pump (1) through adjustment of the speed of theeddy current coupler (3).

Even in those cases where the pressure of the frontal cutter chamber (4)changed owing to a change of the performance of the exhaust pump (6)resulting from a change in the concentration of themuddy slurry, thewater supply pump (1),as hereinbefore noted, is automatically adjustedas to its rotational speed or number of strokes in response to theamount of slurry exhausted by the exhaust pump (6), thereby ensuringthat water in an amount necessary to maintain a proper water head issupplied. In those instances where the emergency shutoff valve (13) isin operation, the rise in water head can be continuously controlled withgreat precision by the pressure transmitter (7) detecting the change inthe water head and by thewater supply pump ('1) responding over broadrange up to the established pressure to be maintained.

Since the controlling system of the present invention is set up ashereinbefore described, it is possible by setting the pressure settingdevice (9) appended to the regulator (8) at a prescribed water pressureand by detecting the fluctuation in water head of the working.

face with said pressure setting device, converting the water headfluctuation to a voltage fluctuation and transmitting this to the eddycurrent coupler, to accomplish minute adjustments in the number ofstrokes or rotational speed of the water supply pump (1) with a promptresponsespeed and thus control the amount of water supplied, which isnecessary for maintaining the water head.

In the case of the method of controlling the water head of the frontalcutter chamber in the conventional pressurized-slurry sealed shieldmethod, the water head that was necessary for maintaining the stabilityof the working face was difficult of maintaining constant at all times.Hence, there was a possibility of the caving in of the working face. Onthe other hand, in accordance I with the present invention, the waterhead can be maintained constantly at the set pressure in accordance withchanges in the concentration of the muddy slurry due to variation in theamounts of the excavated soil, fluctuations in the resistance to flow inthe water supply and exhaust lines due to changes in their lengthaccompanying the progress of the excavation, or changes in theperformance of the exhaust pump due to changes in the concentration ofthe muddy slurry, as well as in those cases where the operation of theexhaust pump ceases for emergency or other reasons. Again, the waterhead can be readily set in accordance with the conditions of the workingface, and hence it becomes possible to carry out the pressurized-slurrysealed shield method of construction safely and with certainty.

I claim:

1. A method of controlling the water head supplied by a pump at theworking face in a pressurized-slurry sealed shield method ofconstruction, said method of controlling the water head comprising thesteps of detecting the water head at the working face with a pressuretransmitter, transmitting said water head as an electric signal to apressure regulator, comparing said electric signal with the set pressureat said regulator, converting the electric signal corresponding to thedeviation between the first-named electric signal and said set pressureto a pressure signal, and transmitting said pressure signal as anexcitation voltage to a variablespeed motor connected to the pumps andmade up of an eddy current coupler and an induction motor to control therotational speed of said variable speed motor, thereby changing theamount of water supplied by the pump.

2. The method according to claim 1 which comprises the steps ofdetecting the number of rotations of said variable-speed motor, feedingback said number of rotations as voltage, comparing said detectedvoltage with the set voltage, and adjusting the excitation voltage untilthe deviation becomes zero, thereby adjusting the number of rotations ofsaid motor.

1. A method of controlling the water head supplied by a pump at theworking face in a pressurized-slurry sealed shield method ofconstruction, said method of controlling the water head comprising thesteps of detecting the water head at the working face with a pressuretransmitter, transmitting said water head as an electric signal to apressure regulator, comparing said electric signal with the set pressureat said regulator, converting the electric signal corresponding to thedeviation between the first-named electric signal and said set pressureto a pressure signal, and transmitting said pressure signal as anexcitation voltage to a variable-speed motor connected to the pumps andmade up of an eddy current coupler and an induction motor to control therotational speed of said variable speed motor, thereby changing theamount of water supplied by the pump.
 2. The method according to claim 1which comprises the steps of detecting the number of rotations of saidvariable-speed motor, feeding back said number of rotations as voltage,comparing said detected voltage with the set voltage, and adjusting theexcitation voltage until the deviation becomes zero, thereby adjustingthe number of rotations of said motor.